A/C pipe was cold only on first start up...then luke warm and later hot. No worky
This may be illegal to do yourself in your country unless you have the correct ticks in various nonsense training boxes, but....
Your symptoms sound like lack of gas to me. You need someone to put some pressure gauges on it.
https://www.ebay.co.uk/itm/403116218375These allow you to measure the gas pressures in the pipes either side of the compressor. With the engine not running, both pressures should be the same - typically 4 or 5 bar IIRC. With the engine running (well compressor running really) then before the compressor the pressure should be low-ish (2-5 bar IIRC), and the pipe will be cold. After the compressor the pressure will be high (20+ bar IIRC), and the pipe will be warm/hot.
If the system is blocked, then you'll end up with very high pressure in the HP side, and less than atmospheric in the LP side. If the system is low on gas, then the compressor can't generate enough differential across the expansion valve to give the required cooling. If the system is empty of gas, then the LP cutoff switches will stop the compressor clutch from engaging.